Decompression Sickness

Description

Multisystemic disease process resulting from escape of inert gas bubbles (nitrogen) out of solution into body fluids and tissues

Etiology

• Pathophysiology:
  • Increases in ambient pressure cause increase in partial pressure of nitrogen inspired (as per Henry law, below)
  • Nitrogen accumulates in tissues in increasing concentrations the longer ambient pressures remain elevated
  • Decompression sickness (DCS) results when ambient pressure keeping nitrogen in solution decreases too rapidly (on ascent), preventing gradual removal of excess body burden of nitrogen
  • As the nitrogen removal gradient is overwhelmed, tissues become supersaturated and bubble formation occurs
• Henry law:
  • Amount of gas that will dissolve in a solution at a given temperature is directly proportional to partial pressure of that gas
  • Increases in partial pressure result in larger amount of gas dissolved in tissue
  • Decreases in partial pressure result in gas coming out of solution
• Bubbles are viewed as foreign material by body inciting inflammatory and coagulation responses
  • Leads to increased vascular permeability and decreased intravascular volume and hemoconcentration
• Bubble location determines clinical effects:
  • Blood flow and lymphatic obstruction leading to ischemia, infarction, or lymphedema
  • Mechanical distention of tissues leading to pain
• Risk factors for DCS:
  • Dive factors:
    • Greater depth
    • Longer bottom time
    • Multiple dives in a day
    • Rapid ascent
    • Cold water
  • Human factors:
    • Obesity
    • Intercurrent illness
    • Pulmonary disease
    • Dehydration
  • Proper use of dive tables and computers does not eliminate risk for DCS
  • Predive vigorous exercise may reduce risk
• 50% of patients develop symptoms in 1 hr, 90% develop symptoms within 6 hr
• Airplane flight following diving can precipitate DCS owing to lower cabin pressure